HEEELLLLPPP!!!

Your supposed to slowly bring it down then after a period of time slowly bring it back up to what your main tank is

 

Exactly! In fact if you think about it a rapid drop in salinity is actually less harmful for fish than a rapid increase. You're screwing with the animals osmotic regulation system, marine fish have to drink lots of water in order to stay hydrated, they expel the salts through specialized glands in order to maintain their internal salinity at less than that of the surrounding solution. A drop in salinity means they expend less metabolic energy expelling ions from the water to remain hydrated, although mechanically water intake may be much the same.
In fact it's highly unnatural for a fish to suddenly experience a rise in salinity, whereas a decrease in salinity may be experienced by in-shore species several times throughout their lives. Just think of a shallow pool or isolated lagoon at low tide, water evaporates for hours in these pools, and in particularly shallow/low volume channels the salinity may increase significantly. The fish are effectively trapped there sometimes during the heat of the day, and gradually the salinity increases, followed by a very rapid decrease back to normal levels when the tide or a swell comes in.

 

I just thought it should be brought up before someone reads this and says, Its been 8 weeks time to put the fish back in the DT and plop them in.

 

I did 5 weeks at 1.009 last fall , let the tank run fallow and have no sign of ich since. But yes, after going thru all that !!!## I will never add another fish without QT first. In my favor I have FW tanks so a seeded filter immediately was no problem. Also in my haste, I plopped them right from the DT to 1.009 with no ill affects. Not recommending this, but wasn't really thinking in my panic but they were fine. I did, however, take the time in raising the SG. that is a must.

 

Does it make sense to send every new fish through hypo salinity before being added to the display?

 

No, not hypo, but QT at 1.025 before adding to DT makes sense to me. Then if you see signs of ich, definitely implement hypo... but if you see no sign of ich after your specified time slot, then your fish will not need to be acclimated.